Bitumen is a bi-product of the distillation of oil, which is widely used in the preparation of asphalts. Bitumen comprises saturated hydrocarbons, aromates, resins and asphaltenes. Asphaltenes are high molecular weight hydrocarbons, the composition of which vary depending on the oil distillation process. The aromates and resins stabilize the asphaltenes by keeping them dispersed in the bitumen.
Current bitumen production differs from the original “straight run” bitumen. The straight run bitumen is a residue of a distilled crude oil. In the past, it was often produced with only one type of crude oil. The last decades the refineries has changed over to other production techniques such as hydro-cracking and crude blending. Because of this, the virgin bitumen does not meet the requirements of the asphalt producers road builders.
More and more bitumen are sold on the market with a high asphaltenes content and low aromatics and resins content (the maltenes). If polymers or waxes are introduced to this type of binder the colloidal stability is disrupted and the bitumen will lose a big part of its properties. When the bitumen becomes unstable the asphalt mix will lose its workability and its cohesion. Furthermore, a significant decrease is observed in the water sensitivity. Adding maltenes will improve the bitumen binder behaviour and will stabilize the asphaltenes. Adding aged asphalt to the asphalt mix with this high asphaltenes content, will have the same result as the addition of polymers or waxes: not only will it make the virgin unstable it will also result in a quicker aging. Accordingly, there is a need methods for modifying virgin bitumen compositions.
Furthermore, bitumen compositions are very sensitive to aging and need to be replaced in time as their properties degrade in the course of time. A common problem is that bitumen compositions become too brittle as a result of which road surfaces deteriorate and need to be renewed every so many years. Since the amount of available and suitable bitumen has been decreasing considerably in recent years, it is also desirable to reuse bitumen compositions. This can be established by recycling the bitumen compositions with or without the addition of fresh bitumen and/or suitable additives.
Examples of known additives to modify bitumen compositions for recycling include for instance mineral oils, paraffin's and rapeseed oil. These additives have, however, the disadvantage that they render the bitumen composition too soft, resulting in for instance asphalts having too high viscous behavior and thus impacting the durability of such asphalts in road applications. Another disadvantage of these additives is that they poorly agree with bitumen compositions as they not only have a bad influence on the colloidal index (CII), but also on the adhesion on the minerals. Other known bitumen modification additives include petrochemical resins but these are very expensive.
An alternative and less costly additive to rejuvenate (recycle) bitumen compositions has been proposed in WO 2010/085140, which describes a method to rejuvenate bitumen-containing compositions by adding to the bitumen-containing compositions a distillation residue of a cashew nut shell liquid (DR-CNSL). Further, WO 2010/110651 discloses another method for rejuvenating a bitumen-containing according to which a raw (untreated) cashew nut shell liquid, which has been heated so as to obtain a technical CNSL (T-CNSL), is added to a bitumen-containing composition. The rejuvenated bitumen-containing compositions obtained in accordance with these two patent specifications, still leave considerable room for improvement.
The present inventors hereby provide an improvement to these previously disclosed methods, by providing a polymerized CNSL, that besides showing an improved effect, also is more reliable and obtainable with a high yield.